Histopathological diagnosis is very important because the result of the diagnosis is involved in determining the subsequent clinical course, for example. In histopathological diagnosis, a tissue collected from a lesion is prepared for a glass slide sample for a microscope, and a pathologist observes the sample and makes diagnosis regarding, for example, whether the lesion is benign or malignant, and the degree of advancement and malignancy. In the diagnosis, pathologists make decisions depending on their experiences in many cases.
In the related art, a pathologist observes the sample through a microscope to make the diagnosis in the pathological diagnosis. However, recently, a method in which the sample image is made into a digital image, and the image is observed through a personal computer or the like to make diagnosis has been put to practical use. This technique makes it possible for a pathologist to make diagnosis while changing magnification of the image and the diagnosis portion in the image through a large screen such as a personal computer, without using a microscope.
In addition, there is a support system for histopathological diagnosis which processes the digitalized pathological images with a computer and thereby enables characteristic useful in the diagnosis to be extracted. The pathologist's decision is the premise of the pathological diagnosis; however, as the image process technique and the optical system technique have advanced, a qualitative diagnosis can be made by using the support system for histopathological diagnosis.
In the histopathological diagnosis, the Hematoxylin-Eosin stain (HE stain) is a basic staining method. In the HE stain, the cell nucleus is stained bluish purple, and cytoplasm and stromal components are stained pale pink with good contrast such that the entire image of the tissue may be properly observed.
Through knowledge of the histopathological diagnosis, it is known that the NC ratio (which is equal to the area of nucleus in a cell/the area of cytoplasm in a cell) of a cancer cell increases remarkably compared to a normal cell. The NC ratio may be calculated by using an image showing hematoxylin distribution and an image showing eosin distribution.
Patent document 1 discloses a diagnosis support system detecting cancer sites from digital pathological image data. In the patent document 1, the distribution of the nucleus and the cytoplasm included in the digital pathological images is found quantitatively by using the NC ratio. Based on the information, the distribution of the cancer site and the degree of advance of cancer is determined.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2004-286666